1. Field of the Invention
The invention relates to a heating rod with a heating element of conductive ceramic material, glow plugs with one such heating rod, and a process for their manufacture.
2. Description of the Related Art
A heating rod with a heating element of conductive ceramic material is known from DE 4117253 A1. Here the heating section aligned unsupported on the tip of a hollow holder to the outside is mounted in a glow plug body, an insulating layer being inserted between the conductor sections which correspond to the front end area of the holder of the ceramic heater and being securely fitted there. The conductor sections and the insulating layer are connected via a brazing solder filler metal which consists of a Cuxe2x80x94Alxe2x80x94Ti alloy. The use of various insulating layers of different materials and the necessity of bonding and binding layers lead to a complex structure of this glow plug.
The primary object of the invention is to make available a heating rod with a heating element of electrically conductive ceramic material and rod glow plugs with one such heating rod, and simple production processes of the heating rod will enable mass production, while at the same time high serviceability and dimensional accuracy as well as a compact design of the heating rod or rod glow plug will be attainable.
This, as well as other objects in accordance with the present invention is achieved by the heating rod with a heating element of electrically conductive ceramic material which has a heating area which is U-shaped in the lengthwise section integrally adjoining a pair of conductors, characterized in that the heating element is embedded in a heating rod body of electrically insulating ceramic mass, the heating element being made as a U-shaped component in the lengthwise section and being produced by an injection molding process, and being extrusion-coated with an insulating ceramic with the formation of the heating rod body.